Fuel reformers, or fuel processors, are capable of converting a hydrocarbon fuel such as methane, propane, natural gas, gasoline, diesel, and the like, into various lower molecular weight gas streams such as hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), nitrogen (N2), and water (H2O), which can be utilized for many beneficial purposes. Fuel reformers can exist in various configurations to accomplish this function, such as, but not limited to, partial oxidation reformers, steam reformers, dry reformers, plasma reformers, and the like.
Partial oxidation reformers can burn a fuel/oxidant mixture in the presence of a catalyst to produce gas stream, such as, carbon monoxide and hydrogen. The reaction is exothermic and temperatures of about 600° C. to about 1,600° C. (degrees Celsius) are experienced during conversion. Catalysts can be employed which promote accelerated conversion of the fuel into the desired effluent. These catalysts can include, but are not limited to; metals of the alkali, alkali earth, lanthanide series, and transitional metals. An example of the partial oxidation reforming reaction is as follows:

Reformers may be used in multiple applications. One such application is within NOx abatement systems for diesel-powered vehicles. In these applications, reformers can be employed to convert liquid fuel into a gas stream that can serve to regenerate various exhaust treatment devices' catalytic substrates.
Partial oxidation reformers (POx) can comprise a mixing zone and a reforming zone. In the mixing zone, an oxidant and a fuel are mixed to form a fuel mixture, which undergoes combustion and conversion within a substrate to produce the desired gas stream within the reforming zone. During operation, the oxidant and fuel mixture (hereinafter referred to as “fuel mixture”) can influence the quality of the gas stream and the reformers' operating conditions, therefore this operating variable is typically controlled during normal operating conditions (steady state conditions). During start-up however, controlling the fuel mixture can be challenging because system sensors are not up to their normal operating conditions, and as a result, closed-loop control is not obtainable. Therefore the fuel mixture can be controlled utilizing calculations based on the reformer's inlet mass air flow-rate and fuel injector pulse width. Unfortunately, inherent measurement errors associated with this method can produce large variations in the fuel mixture, which can produce excessively rich and/or excessively lean conditions. Under excessively rich conditions fuel can pool within the reformer and results in carbon deposition on the internal surfaces of the device, excessively lean conditions can result in high substrate temperatures that result in a decreased working life of the substrate.
Consequently, there is a need for further innovation of fuel reformer fuel mixture control methods that provide enhanced control of the fuel mixture during reformer start-up, without producing conditions conducive to carbon deposition and excessive substrate temperatures.